This invention relates to monitoring an aircraft's acceleration during the takeoff roll up to V1 speed.
Aircraft are certified by a State's aeronautical licensing authority; such as, the United States Federal Aviation Agency, Transport Canada, the British Air Registration Board, or the European joint Aviation Authority.
One of the certification requirements involves the aircraft having adequate takeoff performance, such that, with all engines operating, within the available runway distance, the aircraft is capable or accelerating from a standstill to the takeoff decision speed (commonly referred to as the V1 speed or the Go-NoGo speed, where, in event of an engine failure, the aircraft is capable of either continuing the takeoff safely, or, rejecting the takeoff and stopping within the remaining runway distance available.
The takeoff acceleration is dependent upon eight primary criteria, namely,
a) All-Up Gross Weight of the Aircraft, PA1 b) Altitude of the Airfield, PA1 c) Outside Air Temperature, PA1 d) Runway Slope, PA1 e) Wind Component, PA1 f) Engine Power Setting, PA1 g) Wing Flap Setting, and PA1 h) Runway Contaminants; such as, snow, slush, and standing water.
Aircraft manufacturers produce takeoff performance graphs which, when entered with the appropriate criteria, will show the V1 speed and the runway distance required. During takeoff, the aircraft must maintain an acceleration rate such that V1 will be achieved at, or within, the graphed distance.
Let us consider the position of the pilot who has taxied out from the departure gate and has lined up on the takeoff runway. He knows his V1 speed, and his runway distance required. He commences the takeoff roll. He experiences acceleration that seems satisfactory, but there is no instrumentation system provided to him that directly tells him if the rate of acceleration is in fact satisfactory--that remains, to this day, a "seat of the pants" acquired skill.
Many factors can insidiously retard the required takeoff acceleration rate which may result in having inadequate distance for takeoff, or inadequate distance for the accelerate-stop situation.
Some of the factors that may insidiously retard the required takeoff acceleration rate are: runway contaminants more severe than expected, erroneous engine pressure ratio gauges, engines not delivering rated power, wrong wingflap setting, soft tire(s), dragging brake(s), parking brakes not having been released, etc.